1. Field of the Invention
The invention relates to automated systems for permitting authorized persons to access secured buildings or other areas while preventing such access by unauthorized persons. More particularly, the invention relates to an access control system that uses biometric parameters to identify authorized persons and to permit access by the authorized persons.
2. Description of the Related Art
The invention relates to restricting access into a restricted area and thus the term “access”, as used herein, refers to physical entry into a building, or other restricted area. However, the restricted area can be the exterior of a building or the like and thus the invention can be applied to controlling entry or exit out of a building or other area. There have always been situations in which it was desirable to restrict access to certain physical areas to a select person or group of people. Such restricted access has been accomplished by fences, walls, locks and other barriers. However, even the use of barriers has not prevented unauthorized access. Accordingly, it has been necessary in many instances to provide human surveillance in the form of a security guard at an entrance to an area or through the use of video cameras or the like to transmit images to a security guard at a remote or centralized location. Of course, the use of security guards and video cameras can become expensive and is only as reliable as the particular guard and his state of alertness at any particular time.
The complexities of modern society have only served to increase the need for access control. For example, many government agencies and contractors work on matters that are of a confidential or even “top secret” nature. In fact, most workplaces, such as offices, warehouses, and even retail stores in some instances, have a need to implement access control to prevent the theft of intellectual property and/or goods.
In response to the need for access control, many government agencies and businesses have issued identification cards to their employees and other authorized personnel. Often, the identification card includes a picture of the authorized person. However, such an identification card still requires a security guard or other personnel for verification. Also, such cards are easily forged by replacing the picture with that of an unauthorized person. To overcome these limitations, it is known to provide the employee with a personal identification number (PIN) or other identifying code. The identifying code can be encoded in a magnetic strip or the like in a security card and read by an automated reader at an entrance to grant access only to persons having the card. Alternatively, the code can be entered by the user on a keypad to gain access. However, the use of identifying codes also has drawbacks in access control applications. In particular, the identification card can be stolen or the user can be forced under duress to reveal their code. In such cases, unauthorized possessors of the card or code can gain access to a restricted area.
The use of biometrics has been proposed as a solution to the limitations noted above. Generally, the term “biometrics” refers to the study of measurable biological characteristics, i.e. biometric parameters, of a living being. In the context of security, “biometrics” refers to techniques that rely on a unique, measurable characteristic of a living being for automatically recognizing or verifying identity. Examples of biometric parameters are facial data, retinal data, fingerprint data, speech data, and the like.
Generally, biometric systems operate in the following manner. First, a system captures a sample of at least one biometric parameter during an “enrollment” process. The parameters are then converted by the system into a mathematical code, i.e., data, that is stored as the biometric template representing measured biometric parameters for that person. There may also be a way to correlate the template to the person. For example, a personal identification number (PIN) can be given to an enrolled user, which is entered to access the template. A new biometric sample is then taken and compared to the template or to a group of templates. If one of the templates and the new sample match, the person is recognized as authorized. Central to a biometric system is the “engine” which processes the biometric data in accordance with various algorithms or artificial neural networks.
Some biometric systems use “identification” methods and some use “verification” methods. In identification systems, a sample is presented to the biometric system and the system then attempts to find out who the sample belongs to by comparing the sample with a plurality of templates obtained through enrollment. Verification systems on the other hand perform a one-to-one process where the biometric system is seeking to verify identity. A single biometric sample is matched against a single template obtained during enrollment. If the two match, the system effectively confirms that the person actually is who he presents himself to be. The key difference between these two approaches centers on the logic addressed by the biometric system and how these fit within a given application. Identification systems decide who the person is and can check whether more than one matching biometric template exists. Accordingly, identification systems can deny access to an individual who is attempting to pass himself off with more than one identity. Verification, on the other hand only decides if the person is who he says he is. Accordingly, identification systems are more versatile and powerful. However, verification systems generally require less processing horsepower and thus are commonly used.
In typical biometric access control systems, biometric sensors are placed, proximate entrances and are linked to a central computer having biometric “enrollment” data, i.e., templates, representing biometric parameters of authorized users collected from a central enrollment station. If the biometric parameter collected at the entrance matches a template stored in the central computer, access is granted. However, conventional biometric systems have several limitations. In particular, the sensing accuracy of biometric parameters, such as facial parameters, retinal parameters, and the like is highly dependent on the environment in which the parameters are sensed. For example, the lighting intensity, angle and color will affect sensing of biometric parameters. Accordingly, the ability to reliably match data representing parameters collected at an entrance with data of templates collected during enrollment is limited, especially when the entrance is an external entrance where the weather, season, and time of day will affect lighting significantly. Also, sensing biometric parameters, converting the parameters to data, communicating the data to a central computer, and comparing the data parameters with templates of enrollment data in the central computer is relatively time consuming, even with modern high speed computers and communication links. Accordingly, such systems present significant inconveniences to the authorized persons through improperly rejected access and time delays prior to granting access.
The use of less environmentally affected biometric parameters, such as fingerprint parameters can alleviate some of the problems noted above. However, sensing such parameters requires that the person desiring access make physical contact with a sensor, such as a fingerprint scanner, upon each entry request. Also, such parameters are easily affected by skin debris, and skin blemishes. Therefore, the person desiring access may have to wipe off their finger, not to mention remove any gloves, prior to submitting to the physical contact with the sensor. The match tolerance between a template and data corresponding to a measured parameter can be increased to minimize lockout of authorized users. However, such an approach inherently reduces the accuracy and effectiveness of the system by increasing the likelihood of allowing access to unauthorized users.
U.S. Pat. No. 5,802,199 attempts to solve the issue of slow response in biometric identification systems by transmitting a subset of templates obtained through enrollment from a central computer to one of plural “local” computers. If the user attempts to use an ATM terminal that corresponds to the “local” computer, identification is accomplished by collection of biometric data and a PIN number and by comparison with templates in the “local” computer. If a matching template and PIN number is not in the “local” computer, biometric identification is accomplished in the central computer by transmitting collected data over a remote communication link.
U.S. Pat. No. 5,802,199 relates to identification for allowing use of ATM terminals and not for access control as defined herein. The practical communications of access control and ATM use control are quite different. For example, the “local” computers disclosed in U.S. Pat. No. 5,802,199 are apparently not at the location of biometric sampling, i.e. the ATM terminal. It appears that plural ATM terminals are assigned to each local computer because of the inherent geographic distribution of ATM terminals. The “local” computers are actually centralized computers. Accordingly, the system disclosed in U.S. Pat. No. 5,802,199 is not suitable for high speed access control which generally requires high speed identification within a relatively small geographic area, such as a single building or campus. Also, since enrollment is conducted centrally, i.e. not at the site of the ATM terminal, environmental variables will affect the accuracy of identification. Finally, this system requires that two separate things be recognized, the biometric sample parameters and a PIN number entered by the user.
U.S. Pat. No. 5,903,225 discloses an access control system in which data is encoded on a card during an enrollment procedure in correspondence to the person's fingerprint. When attempting to gain access to a restricted area, a transmitter on the card transmits the data to a receiver at the entrance to grant access. This system apparently does not implement biometric recognition or identification and thus has the same limitations as conventional access systems using magnetic cards. In particular, whoever possesses the card is granted access regardless of their identity.
U.S. Pat. No. 4,993,068 discloses an access system in which the enrollment procedure includes recording biometric data on a card to be carried by the user and comparing the data on the card with data of biometric parameters measured at the entrance. This system is inherently a verification system and thus is not as flexible as an identification system for the reasons discussed above. Also, since enrollment is conducted at a central location, sensing of parameters upon access can be affected by the environment at the entrance. Accordingly, the accuracy of this system is limited.